Process and apparatus for making pulp from fibrous material



Julie 23, 1927. 1,633,735

F. K. FISH, JR

PROCESS AND APPARATUS FOR MAKING PULP FROM FIBROUS MATERIAL Filed July 15 1925 INVENTO 1 F11 fzlyfi, 7'

A TTORNEYS.

Patented June 28,- 1927.

PATENT OFFICE.

UNITED STATES FREDERICK KNAPP FISH, JR., 0]? SANfFRANCISCO, CALIFORNIA.

Application filed July 15, 1925. Serial No. 43,852.

This invention relates to a process and apparatus for making pulp from fibrous material, and more particularly to the circulation of the digesting or cooking liquor used and the mixing of such liquor with the gases and vapors evolved in the treatment of the material.

Various processes and apparatus for treating such materials are Well known in the art, and while this invention is applicable to niany, or all of them, it is particularly suitable for use'in connection with the processes defined in prior applications for patents filed by me.

In these previous applications I' have fully set forth the value of the gases and volatile solvent extractives evolved by the liquor and material in processes of digesting such materials. It is an'object ofthis invention to provide a process and apparatus in which the usefulness of such gases and volatile solvent extractives is enhanced in order that the effectiveness and speed of the digestive operation may be promoted. I

A further object of this invention is to provide a process and apparatus for mixing thegases and volatile solvent extractives V with the digesting liquoras these. are evolved in the digesting operations.

A still further object of the process and apparatus of this invention is to circulate the digesting liquor mixed with the gases and volatile solvent extractives and to apply the mixture (in a heated condition) to the material under treatment.

A detailed description of the process and apparatus of the invention will now be given with reference to the accompanying drawing in which a preferred form of the apparatus is shown in elevation.

In the drawing, 1 is a digester of usual construction in which the material is treated with the desired cooking liquor. In the upper portion of the digester, means 2 is provided for producing a vacuum in the digester and removing air from the material under treatment. 'A suitable screen 3 is Secured to the means 2 to prevent the entrance thereto of chips or portions of the fibrous material. A pipe 4 having a valve 5 is connected at its upper end with a perforated hood 6 and at its lower end with a pump 7 which discharges into a heater 8. The pipe 9 containing the valve 10 connects the heater with the lower endof the digester. The hood 6 is only partially immersed in mitting the mixture and withdrawal of the gases, volatile solvent extractives and the liquor. In order to accomplish this result it is necessary that the hood be at all times partially submerged in the liquor, and that it be so proportioned with reference to the perforations and the proportion of the capacity of the pump, that only a limited supply of the liquor will be drawn into the pipe 4. When the parts are so proportioned, the pump will draw both gases, volatile solvent extractives and liquor from the di ester, as stated.

Tn the operation of this invention, air is removed from the fibrous material with which the digester is charged to reduce the is started in the usual way. Gases and volatile solvent extractives are evolved and collected in the space above the liquor in the digester and; periodically, or continuously these are removed together with a portion of the liquor by the'operation of the pump 7. This mixture of gases, volatile solvent extractives and liquor is simultaneously returned to the lower portion of the digester to cause a circulation of the treating fluid in the digester and assist in maintaining pressure therein. The temperature of the mix-- ture of fluid and liquor withdrawn from the upper portion of the digester is raised in the heater 8 and thus the circulation of the liquor thus heated secures and maintains the required temperature in the di ester.

It will be apparent that the withdrawal of Y fluid from the space in the digester above the liquor tends to promote the volatilization of further portions of the treating liquor and volatile. solvent extractives of the fibrous material, making these further portions available for circulation and reuse in the cook in solution in the liquor or in gaseous form. I

Moreover it will be obvious that when the liquor level in the digester is below the lower end of the hood 6, gases and volatile ex-- tractives only will be withdrawn from the digester by the pump and the temperature of such gases will be raised in the heater 8 and be returned to the digester without condensation or separation.

the lower portion of the digester for use in the same cook.

2. The process of making pulp from fibrous materlal as defined in claim 1, wherein the withdrawn fluid is heated before being returned to the digester.

3. The process of making pulp from fibrous material, consisting in cooking the material with a highly heated liquor under pressure in a digester, with a space above the body of liquor in the digester simultaneously mixing and removing gases and volatile solvent extractivcs from said space and liquor in liquid form from the digcster, further mixing the gases and liquor and returning the mixture to the lower portion of the digester for use in the same cook.

4. The process of making pulp as defined in claim 3, wherein the mixture of gases, volatile extractives and liquor is heated and returned to the digester in a highly heated condition to enrich the liquor with volatile extractives and gases and maintain the temperature of the cooking liquor at the desired point.

5. In a process of making pulp the step which consists in removing volatile solvent extractives produced from the Wood from the upper portion of the digester and Without condensation or separation returning them to the lower portion of the digester for further use in the cook.

6. An apparatus for producing pulp from librous material which consists of a digester, means for reducing the pressure below atmospheric in said digcster, and means for mixing and withdrawing gases, volatile extract-ives produced from the Wood and liquor from the upper portion of the digester and returning the gases and liquor in a mixed condition to the lower portion of the digester without exposure to the atmosphere.

In testimony whereof I aflix my signature.

FREDERICK KN'APP FISH, JR. 

